Anchor assemblies in stretch-resistant vaso-occlusive coils

ABSTRACT

Vaso-occlusive devices are provided for occluding an aneurysm within the human vasculature. The vaso-occlusive device also includes a stretch-resisting member that extends through at least a portion of a lumen of the primary coil and is directly or indirectly attached to the primary coil at two locations axially separated from each other to prevent or minimize axial stretching of the primary coil. At one location, the stretch-resisting member is coupled to the primary coil via a flexible anchor assembly disposed within the lumen. In one embodiment, the anchor assembly may comprise an anchor coil and a link directly or indirectly coupled between the anchor coil and the stretch-resisting member. Alternatively, the anchor assembly may comprise a chain of twisted links.

RELATED APPLICATIONS

The present application is a continuation of pending U.S. patentapplication Ser. No. 11/618,362, filed Dec. 29, 2006, which is acontinuation of application Ser. No. 10/185,650, filed on Jun. 27, 2002,now U.S. Pat. No. 7,166,122, which is related to application Ser. No.10/185,671, now U.S. Pat. No. 7,485,122, and Ser. No. 10/185,669, nowabandoned, both of which were filed on Jun. 27, 2002, and are herebyfully and expressly incorporated herein by reference.

FIELD OF THE INVENTION

The field of the invention relates to implantable vaso-occlusivedevices, and more particularly, to stretch-resistant vaso-occlusivecoils.

BACKGROUND OF THE INVENTION

Vaso-occlusion devices are surgical implements or implants that areplaced within the vasculature of the human body, typically via acatheter, to block the flow of blood through a vessel or an aneurysmstemming from the vessel via the formation of an embolus. One widelyused vaso-occlusive device is a helical wire coil having windings thatmay be dimensioned to engage the walls of an aneurysm. Virtually allsuch vaso-occlusive implants are delivered by pushing the devicesthrough wire-guided catheters.

As an example of an early vaso-occlusive device, U.S. Pat. No.4,994,069, to Ritchart et al., describes a vaso-occlusive coil thatassumes a linear helical configuration when stretched and a folded,convoluted configuration when relaxed. The coil assumes the stretchedcondition during delivery of the coil at the desired site by passagethrough the catheter, and assumes the relaxed configuration, which isbetter suited to occlude the aneurysm, once the device is so placed.Ritchart et al. describes a variety of secondary shapes, including“flower” shapes and double vortices. A random secondary shape is alsodescribed. Vaso-occlusive coils having little or no inherent secondaryshape have also been described. For instance, in U.S. Pat. No.5,690,666, to Berenstein et al., is found a coil having little or noshape after introduction into the vascular space.

Vaso-occlusive coils having materials added externally to the coil toenhance its therapeutic effect have also been manufactured. For example,vaso-occlusive coils having attached fibrous elements in a variety ofsecondary shapes are shown in U.S. Pat. No. 5,304,194. A vaso-occlusivecoil with a fibrous woven or braided covering of a filamentary materialis described in U.S. Pat. No. 5,382,259. And vaso-occlusive coils havinga polymeric fiber wrapped around the wire of the primary coil or apolymeric covering wrapped around the primary shape of the coil areshown in U.S. Pat. No. 6,280,457.

There are a variety of ways of discharging shaped coils and linear coilsinto the human vasculature. In addition to those patents that apparentlydescribe only the physical pushing of a coil out into the vasculature(e.g., Ritchart et al.), there are a number of other ways to release thecoil at a specifically chosen time and site. U.S. Pat. No. 5,354,295 andits parent, U.S. Pat. No. 5,122,136, both to Guglielmi et al., describean electrolytically detachable embolic device. In addition, avaso-occlusive device with multiple detaching points was described inU.S. Pat. No. 5,941,888 to Wallace et al. A variety of mechanicallydetachable devices are also known, examples of which are disclosed inU.S. Pat. No. 5,234,437, to Sepetka, U.S. Pat. No. 5,250,071, toPalermo, U.S. Pat. No. 5,261,916, to Engelson, U.S. Pat. No. 5,304,195,to Twyford et al., U.S. Pat. No. 5,312,415, to Palermo, and U.S. Pat.No. 5,350,397, to Palermo et al.

Vaso-occlusive coils containing a means for preventing the stretching ofthe coil during movement of that coil are also known. For instance, inU.S. Pat. No. 5,833,705, to Ken et al., an implantable vaso-occlusivedevice is described in which a stretch-resisting member extends throughthe lumen of the outer helical coil and is attached to the coil at twolocations. The stretch-resisting members can be made from polymericfilaments or other flexible materials. In U.S. Pat. No. 6,193,728, toKen et al., a stretch-resistant vaso-occlusive coil is described inwhich the stretch-resisting member is indirectly attached to the coilvia an anchor coil coaxially situated between the outer coil and thecore wire. During manufacture of the coil assembly, which preferablyinvolves the application of heat, care must be taken to avoid meltingthe polymeric filaments of the stretch-resisting member.

In another variation of the vaso-occlusive coil, instead of the anchorcoil, a single twisted link, which has a loop at the distal end toconnect with the stretch-resisting member, is utilized as the anchoringdevice in an attempt to distance the polymeric filament from the heatedproximal end. Although this embodiment is successful in preventing thefilament from melting, the single twisted link creates a stiff sectionat the proximal end of the coil. This stiff section can cause problemsduring placement of the coil in the aneurysm by preventing the proximalend from curving into the interior of the aneurysm. Rather, the stiffproximal end could extend through the mouth of the aneurysm into theparent artery where vaso-occlusion is not desired. In addition, thetwisted anchor, with its relatively large diameter, is difficult toinsert into vaso-occlusive coils with smaller lumens.

Accordingly, improved vaso-occlusive devices utilizing more flexibleanchoring assemblies for the stretch-resisting member are desired.

SUMMARY OF THE INVENTION

The present inventions are directed to a vaso-occlusive device that canbe deployed within the vasculature of a patient to occlude the flow ofblood therein. Preferably, the inventive vaso-occlusive device isdeployed to provide emboli in aneurysms located within the vasculaturesof humans, but may also be used at any site in a human or animal thatrequires occlusion. In providing occlusion, the vaso-occlusive deviceincludes a primary coil that can be deployed into one of any variety ofsecondary shapes to conform to the occlusion site. The inventivevaso-occlusive device can be carried to the target site using a deliverydevice and released therefrom using any one of a variety of detachablemeans, such as an electrolytic joint. The vaso-occlusive device alsoincludes a stretch-resisting member that extends through at least aportion of a lumen located within the primary coil. Thestretch-resisting member is directly or indirectly coupled to theprimary coil to prevent or minimize axial stretching of the primarycoil. At one of the locations, the stretch-resisting member is coupledto the primary coil via an anchor assembly disposed within the coillumen. By way of non-limiting example, the anchor assembly can belocated at the proximal end of the primary coil, and thestretch-resisting member can be affixed, either directly or indirectly,between the distal end of the primary coil or some other location on theprimary coil and the proximally located anchor assembly.

In accordance with a first aspect of the invention, the anchor assemblycomprises one or more flexible joints. In the preferred embodiment, theanchor assembly also comprises a plurality of rigid members betweenwhich the flexible joints are disposed. For example, if the anchorassembly includes first and second rigid members, a single flexiblejoint may be located therebetween. The first rigid member may bedirectly or indirectly coupled to the outer primary coil and the secondrigid member may be directly or indirectly coupled to thestretch-resisting member.

Although the present invention should not necessarily be limited by thisadvantage, the presence of the flexible joint(s) provide the desiredflexibility for the proximal end of the primary outer coil, while alsohaving a sufficient length to locate the stretch-resisting member awayfrom any heat generated at the proximal end of the primary coil duringthe manufacturing process. By way of non-limiting example, the rigidmembers may be an anchor member (such as, e.g., a tubular member oranchor coil) and a link. The anchor assembly may also comprise a chainof links, each of which is twisted in order to maintain the axialstrength of the anchor assembly. But the invention in its broadest senseshould not be limited to an anchor coil and link or a chain of twistedlinks.

In accordance with a second aspect of the invention, the anchor assemblycomprises an anchor coil and a link directly or indirectly coupledbetween the anchor coil and the stretch-resisting member. By way ofnon-limiting example, the distal and proximal ends of thestretch-resisting member can be respectively affixed to the distal endof the primary coil and the link. Filler material, such as, e.g.,polyethyleneterephthalate (PET), polyamide, silicon, or polyurethane canbe used to provide structural integrity to the proximal end of theprimary coil where the anchor coil is affixed within the primary coillumen. The link can be composed of any suitable biocompatible material,but in the preferred embodiment, platinum is used.

Although the present inventions should not necessarily be limited bythis advantage, the presence of the link allows the stretch-resistingmember to be located away from any heat generated at the proximal end ofthe primary coil during the manufacturing process. The flexibleconnection between the anchor coil and the link, provide the desiredflexibility for the proximal end of the primary coil. By way ofnon-limiting example, the length of the anchor coil, having a preferablelength of 1.0 mm, and link combination can be reduced to about 1.8 mmfrom 2.6 mm. The length of the link can be less than 1 mm.

In accordance with a third aspect of the invention, the anchor assemblycomprises an anchor chain comprising a proximal twisted link and adistal twisted or untwisted link, which is directly or indirectlycoupled to the stretch-resisting member. The presence of the distal linkallows the length of the proximal twisted link to be reduced, whilelocating the stretch-resisting member away from any heat generated atthe proximal end of the primary coil during the manufacturing process.The reduction in the length of the relatively stiff proximal link, andthe flexible connection between the proximal link and the distal link,provide the desired flexibility for the proximal end of the primarycoil. By way of non-limiting example, the distal and proximal ends ofthe stretch-resisting member can be respectively affixed to the distalend of the primary coil and the distal link. By way of non-limitingexample, a proximal twisted link having a preferable length of 2.6 mmcan be reduced to about 1.2 mm, while the length of the distal link canbe less than 1 mm. In the preferred embodiment, the anchor chain onlyincludes the proximal and distal links, but can include additional linksas well depending on the desired flexibility and length of the anchorchain. Filler material, such as, e.g., PET, polyamide, silicon, orpolyurethane, can be used to provide structural integrity to theproximal end of the primary coil where the proximal link may be affixedwithin the primary coil lumen in the absence of an anchor coil. Theanchor chain can be composed of any suitable biocompatible material, butin the preferred embodiment, platinum is used.

Although the present inventions should not necessarily be limited bythis advantage, the presence of an anchor chain eliminates the need fora single piece proximal anchor, e.g., an anchor coil, or at the least,allows the length of the anchor coil to be reduced, while locating thestretch-resisting member away from any heat generated at the proximalend of the primary coil during the manufacturing process. Theelimination or reduction in the length of the relatively stiff anchorcoil, and the flexible connections formed by the anchor chain, providethe desired flexibility for the proximal end of the primary coil. By wayof non-limiting example, a 2.6 mm single piece proximal anchor can bereplaced with a 2.4 mm anchor chain, with each of the proximal anddistal links being about 1.2 mm. The lengths of the respective proximaland distal links, however, need not be the same. For example, the distallink can be smaller than the proximal link.

In accordance with a fourth aspect of this invention, the anchorassembly comprises a helical structure directly or indirectly coupled tothe stretch-resisting member. In the preferred embodiment, the helicalstructure takes the form of an anchor coil. Other types of helicalstructures, such as threads on a cylindrical element, can also be used.By way of non-limiting example, the proximal end of thestretch-resisting member can be respectively affixed to the distal endof the anchor coil. The anchor coil is fixedly coupled to the outer coilby situating the windings of the anchor coil between the windings of theprimary coil. In the case of a threaded cylindrical element, the threadsare situated between the winding of the primary coil. In the preferredembodiment, each of the windings of the anchor coil can be disposedbetween adjacent windings of the primary coil. Alternatively, multiplewindings, e.g., a winding pair, of the anchor coil can be disposedbetween adjacent windings of the primary coil. Even more alternatively,multiple windings of the primary coil can be disposed between adjacentwindings of the anchor coil.

There are a variety of ways that the anchor coil and primary coil can beformed and incorporated into the vaso-occlusive device. For ease ofassembly and to minimize the exertion of axial stress on the windings ofthe anchor and primary coils, the windings of the anchor and primarycoils can be open-pitched. For example, a preferred method comprisesmaking the outer primary coil by winding a first wire into a firsthelical coil so that the proximal end of the first helical coil hasopen-pitched windings, and making the anchor coil by winding a secondwire into a second helical coil so that the second helical coil hasopen-pitched windings. The anchor coil is then incorporated into theprimary coil, e.g., screwing, such that the open-pitched windings of theanchor coil are disposed between adjacent open-pitched windings of theprimary coil.

In the preferred embodiment, the entirety of the anchor coil hasopen-pitched windings. It should be noted, however, that only the distalend of the anchor coil or otherwise the portion of the anchor coil thatis incorporated into the primary coil may have the open-pitchedwindings. The windings of the anchor coil can be single winding openpitched, double winding open pitched, or any other multiple-winding openpitched. Alternatively, the windings of the primary coil can be singlewinding open pitched, double winding open pitched, or any othermultiple-winding open pitched. The distal end of the anchor coil may betapered to facilitate incorporation into the primary coil.

Although the present invention should not necessarily be limited by thisadvantage, the incorporation of the anchor coil into the primary coildecreases the wall thickness of the proximal end of the vaso-occlusivedevice, thereby providing the desired flexibility for the proximal endof the primary outer coil, while also locating the stretch-resistingmember away from any heat generated at the proximal end of the anchorcoil during the manufacturing process.

In accordance with a fifth aspect of this invention, the vaso-occlusivedevice includes a plurality of primary coils, a plurality ofstretch-resisting members extending through at least portions of therespective primary coils, and one or more detachable joints locatedbetween adjacent primary coils. The distal and proximal ends of thestretch-resisting member can be respectively affixed to anchorassemblies, such as, e.g., those previously described, located at one orboth of the distal and proximal ends of each primary coil.

Although the present inventions should not necessarily be limited bythis advantage, the presence of multiple detachment means allows for thedeployment of vaso-occlusive devices with selectable length. Thisenables physicians to select the length of the deployed vaso-occlusivedevice as desired in light of the condition and size of the aneurysmbeing treated. The use of anchor assemblies to couple thestretch-resisting member to the primary outer coil segments allows thestretch-resisting member to be located away from any heat generated atthe proximal end of the primary coil during the manufacturing process.

BRIEF DESCRIPTION OF THE FIGURES

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not, therefore, to be considered limiting of itsscope, the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 shows a side view, partial cutaway of a vaso-occlusive assemblyconstructed in accordance with a preferred embodiment of the presentinventions;

FIG. 2A shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 1, particularly showing one embodiment of an anchorassembly constructed in accordance with the present inventions;

FIG. 2B shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 1, particularly showing another embodiment of an anchorassembly constructed in accordance with the present inventions;

FIG. 2C shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 1, particularly showing another embodiment of an anchorassembly constructed in accordance with the present inventions;

FIG. 2D shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 1, particularly showing another embodiment of an anchorassembly constructed in accordance with the present inventions;

FIG. 3 shows a side view, partial cutaway of a vaso-occlusive assemblyconstructed in accordance with another preferred embodiment of thepresent inventions;

FIG. 4A shows a side view of one embodiment of a primary coil that canbe used in the anchor assembly of FIG. 5A;

FIG. 4B shows a side view of one embodiment of an anchor coil that canbe used in the anchor assembly of FIG. 5A;

FIG. 4C shows a side view of one embodiment of a primary coil that canbe used in the anchor assembly of FIG. 5B;

FIG. 4D shows a side view of one embodiment of an anchor coil that canbe used in the anchor assembly of FIG. 5B;

FIG. 5A shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 3, particularly showing one embodiment of an anchorassembly constructed in accordance with the present inventions;

FIG. 5B shows a longitudinal sectional view of the vaso-occlusiveassembly of FIG. 3, particularly showing another embodiment of an anchorassembly constructed in accordance with the present inventions; and

FIG. 6 shows a side view, partial cutaway of a vaso-occlusive assemblyconstructed in accordance with another preferred embodiment of thepresent inventions;

FIGS. 7A-7E show longitudinal sectional views of the vaso-occlusiveassembly of FIG. 6, each particularly showing a variation of an anchorassembly; and

FIGS. 8A-8C show a procedure for delivering the vaso-occlusive assemblyof FIG. 1 into an aneurysm; and

FIGS. 9A-9C show a procedure for delivering the vaso-occlusive assemblyof FIG. 6 into an aneurysm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a vaso-occlusive assembly 100 constructed inaccordance with one preferred embodiment is illustrated. Thevaso-occlusive assembly 100 includes a delivery device comprising a corewire 114 disposed within an elongate tubular catheter 117, and avaso-occlusive device 101 detachably associated with the distal end ofthe delivery device 116 via use of detachable means 112 formed at theend of the core wire 114. In the illustrated embodiment, the detachablemeans 112 is an electrolytic severable joint, as will be described infurther detail below. Other types of detachable means, such asmechanical, can be used to connect the vaso-occlusive assembly 100 tovarious other delivery devices. Thus, it can be appreciated that thevaso-occlusive device 101 can be associated with delivery devices otherthan those that use core wires.

The vaso-occlusive device 101 includes an outer primary coil 102, whichhas a proximal end 104, a distal end 106, and a lumen 105 extendingtherethrough between the proximal and distal ends 104 and 106. Thevaso-occlusive device 101 further includes a stretch-resisting member108, which extends through the coil lumen 105 and is secured to theprimary coil 102 at two locations to prevent axial stretching of theprimary coil 102. Specifically, the proximal and distal ends of thestretch-resisting member 108 are respectively affixed to the proximaland distal ends 104 and 106 of the primary coil 102. Alternatively, thestretch-resisting member 108 only extends through a portion of the lumenand is attached to the primary coil 102 at a location between theproximal and distal ends 104 and 106 of the primary coil 102.

The distal end of the stretch-resisting member 108 may be secured to thecoil 102 by melting, gluing, or otherwise fixedly attaching thestretch-resisting member 108 to the coil 102, either at the distal end106 or some location between the ends of the coil 102. In theillustrated embodiment, the distal end of the stretch-resisting memberis glued or melted and reformed into a distal cap 107, the diameter ofwhich is larger than the inner diameter of the coil 102. Alternatively,the stretch-resisting member 108 may be tied in a knot (not shown),which may or may not be attached to the primary coil 102. These methodsof attachment are disclosed in more detail in U.S. Pat. No. 5,582,619,the entirety of which is herein expressly incorporated by reference. Atthe proximal end 104, the vaso-occlusive device 101 includes an anchorassembly 109 mounted within the lumen 105. The proximal end of thestretch-resisting member 108 is indirectly attached to the proximal end104 of the primary coil 102 through the anchor assembly 109. The anchorassembly 109 comprises a plurality of rigid members and one or moreflexible joints that are situated between the rigid members to provideflexibility to the proximal end 104 of the vaso-occlusive device 101while maintaining separation between the stretch-resisting member 108and the proximal end 104 of the primary coil 102. As will be describedin further detail below, the rigid members of the anchor assembly 109may comprise an anchor coil with an attached link or a chain of links,both of which advantageously maintain the flexibility of the proximalend 104. It should be noted that for the purposes of this specification,a “flexible joint” is any joint the location at which the anchorassembly 109 will tend to bend in the presence of a transversely appliedforce.

In one preferred embodiment, the vaso-occlusive device 101 is adapted toaccept the electrolytically severable joint 112. The delivery device 116in this variation has, except for the severable joint 112 that isintended to be the site of electrolysis, an insulating layer 115 that isdisposed on and continued to the end of the core wire 114 where itconnects with the coil device 101. The insulating layer 115 may bepolytetrafluoroethylene (e.g., Teflon), polyparaxylxylene (e.g.,Parylene), polyethyleneterephthalate (PET), polybutyleneterephthalate(PBT), cyanoacrylate adhesives, or other suitable insulating layer, butpreferably is polymeric, and most preferably is Teflon. Theelectrolytically severable joint is discussed in detail in U.S. Pat. No.5,354,295 and its parent, U.S. Pat. No. 5,122,136, both patents toGuglielmi and Sepetka, described above, and herein expresslyincorporated by reference. It should be noted that other mechanisms fordetaching the vaso-occlusive coil may be used. For example, thevaso-occlusive device may be mechanically deployed. Various mechanicalmechanisms are described in U.S. Pat. Nos. 5,234,437; 5,250,071;5,261,916; 5,304,195; 5,312,415; and 5,350,397, the entirety of whichare herein expressly incorporated by reference.

The materials used in constructing the primary coil 102 may be any of awide variety of materials, and preferably, a radio-opaque material suchas a metal or a polymer. Suitable metals and alloys for the wire makingup the primary coil 102 include the Platinum Group metals, especiallyplatinum, rhodium, palladium, rhenium, as well as tungsten, gold,silver, tantalum, and alloys of these metals. In addition to beinglargely biologically inert, these metals have significant radio-opacityand their alloys may be tailored to accomplish an appropriate blend offlexibility and stiffness. Highly preferred is a platinum/tungstenalloy, e.g., 8% tungsten and the remainder platinum.

The primary coil 102 may also be made of radiolucent fibers or polymers(or metallic threads coated with radiolucent or radio-opaque fibers)such as Dacron (polyester), polyglycolic acid, polylactic acid,fluoropolymers (polytetrafluoroethylene), Nylon (polyamide), or evencotton or silk. If a polymer is used as the major component of theprimary coil 102, it is desirably filled with some amount ofradio-opaque material such as powdered tantalum, powdered tungsten,bismuth oxide, barium sulfate, and the like.

When manufacturing the primary coil 102, the coil material is wound intoa coil, which will typically be linear. Generally speaking, when thecoil 102 is a metallic coil made from a platinum alloy or asuper-elastic alloy such as titanium/nickel alloy, known as “nitinol”.The diameter of the wire used in the production of the coils ispreferably in the range of 0.00025 and 0.006 inches. The coil preferablyhas a primary diameter of between 0.003 and 0.025 inches, but for mostneurovascular applications, a diameter between 0.008 to 0.018 inchesprovides sufficient hoop strength to hold the primary coil 102 in placewithin the chosen body site, lumen, or cavity, without substantiallydistending the wall of the site and without moving from the site as aresult of the repetitive fluid pulsing found in the vascular system.

The axial length of the coil wire will usually fall in the range of 0.5to 100 cm, more usually 2.0 to 40 cm. Depending upon usage, the coil maywell have 10-75 turns per centimeter, preferably 10-40 turns percentimeter. All of the dimensions here are provided only as guidelines,and the invention, in its broader aspects, should not be limitedthereto. Only dimensions that are suitable for use in occluding siteswithin the human body,-however, are included in the scope of thisinvention.

Depending on the desired therapeutic effect and the shape of the site tobe treated, the primary coil 102 may later be treated or accessorized innumerous ways in order to enhance its therapeutic effect. The primarycoil 102 may be made to form various secondary shapes, often through theuse of heat treatment, that may be better suited to fill a particulartreatment site, as disclosed in U.S. Pat. Nos. 5,853,418 and 6,280,457,the entireties of which are expressly incorporated herein by reference.Alternatively, the coil 102 may have little or no shape afterintroduction into the vascular space, as disclosed in U.S. Pat. No.5,690,666, the entirety of which is expressly incorporated by referenceherein. In addition, external materials may be added to the outside ofthe primary coil 102 in an effort to increase its thrombolyticproperties. These alternative embodiments are disclosed in U.S. Pat.Nos. 5,226,911; 5,304,194; 5,549,624; and 5,382,259; the entireties ofwhich are expressly incorporated herein by reference, and U.S. Pat. No.6,280,457, the entirety of which has previously been incorporated byreference.

In a preferred embodiment, the stretch-resisting member 108 is fibrousand desirably polymeric. Suitable polymeric materials can be eitherthermosetting or thermoplastic and can comprise a bundle of threads or asingle filament. Thermoplastics are preferred because they allowsimplification of the procedure for constructing the assembly 100 sincethey may be melted and formed into the distal cap 107. Simple tools,such as soldering irons, may be used to form the distal cap 107.Thermosetting plastics would typically be held in place by an adhesive.Suitable polymers include most biocompatible materials that may be madeinto fibers, including thermoplastics, e.g., polyesters such aspolyethyleneterephthalate (PET), especially Dacron; polyamides,including the Nylons; polyolefins, such as polyethylene, polypropylene,polybutylene, their mixtures, alloys, block, and random copolymers;polyglycolic acid; polylactic acid; fluoropolymers(polytetrafluoroethylene) or even silk or collagen. Thestretch-resisting polymer may be made from materials used as dissolvablesutures, for instance, polylactic acid or polyglycolic acid, toencourage cell growth in the aneurysm after their introduction. Highlypreferred is polypropylene, for instance, in the form of 10-0 and 9-0polypropylene suture material. The diameter of the polymer is typicallybetween about 0.0001 inches and about 0.01 inches.

In some variations of the invention, the stretch-resisting member 108may be composed of any of a wide variety of stainless steels if somesacrifice of radio-opacity and flexibility can be tolerated.Stretch-resisting members of this type are described in U.S. Pat. No.5,853,418. Very desirable materials of construction, from a mechanicalpoint of view, are materials that maintain their shape despite beingsubject to high stress. Certain “super-elastic alloys” include variousnickel-titanium alloys (48-58 atomic % nickel and optionally containingmodest amounts of iron); copper/zinc alloys containing 1-10 weight % ofberyllium, silicon, tin, aluminum, or gallium; or nickel/aluminum alloys(36-38 atomic % aluminum). Particularly preferred are the alloysdescribed in U.S. Pat. Nos. 3,174,851; 3,351,463; and 3,753,700.Especially preferred is nitinol. These are very sturdy alloys that willtolerate significant flexing without deformation even when used as verysmall diameter wire. If a super-elastic alloy such as nitinol is used inthe stretch-resisting member 108, the diameter of the wire may besignificantly smaller than that used when the relatively more ductileplatinum or platinum/tungsten alloy is used as the material ofconstruction.

In one preferred embodiment of a vaso-occlusive device 101(1), as seenin FIG. 2A, the stretch-resisting member 108 is connected indirectly tothe proximal end 104 of the primary coil 102 through an anchor assembly109(1), comprising an anchor coil 150 and an attached link 152. Theanchor coil 150 is coaxially situated in the coil lumen 105. As shown inFIGS. 2A and 2B, the anchor coil 150 and the primary coil 102 areconfigured such that when the anchor coil 150 and the primary coil 152are aligned along a central axis of the vaso-occlusive device 101(1),the outer-most surface of the anchor coil 150 and the inner-most surfaceof the primary coil 102 are radially spaced from one another such thatthe radial space is devoid of material. In the illustrated embodiment,the anchor coil 150 is preferably less than 2.6 mm long, preferablyabout 1.0 mm long.

A loop 154, formed from the final turn or half-turn of the anchor coil150, is connected to the link 152, which is then connected to thestretch-resisting member 108. The stretch-resisting member 108 may beattached to the link 152 through any appropriate means, includinglooping the stretch-resisting member 108 through or around theadditional link 152 or tying the stretch-resisting member 108 to thelink 152. The link 152 is sealed by heating/welding the wire to closethe loop, preferably forming a ball 156 at the sealed junction 155.Alternatively, the link 152 may be laser cut. In the illustratedembodiment, the link 152 may be shorter in length than the anchor coil150, preferably less than 1 mm, e.g., about 0.8 mm long. The link 152can be made of the same materials used to make the primary coil 102,including the Platinum Group metals, especially platinum, rhodium,palladium, rhenium, as well as tungsten, gold, silver, tantalum, andalloys of these metals. Suitable polymers may also be used. Theseinclude most biocompatible materials that may be made into fibers,including thermoplastics, e.g., polyesters such as Dacron; polyamides,including the Nylons; polyolefins, such as polyethylene, polypropylene,polybutylene, their mixtures, alloys and block. The relatively shortanchor coil 150 and the corresponding flexible connection between theanchor coil 150 and the link 152, provide for additional flexibility ofthe primary coil 102 at the proximal end 104.

In this preferred embodiment, a filler material 158 is placed in thecoil lumen 105 for stabilization and to attach the primary coil 102 tothe core wire 114. The filler material 158 preferably comprises athermoplastic formed into place or an epoxy or the like and adheres inturn to both the anchor assembly 109(1) and the core wire 114.Preferably, the filler material 158 is insulative. The filler material158 preferably comprises PET, polyamide, silicon, or polyurethane. Thecore wire 114 is attached to the vaso-occlusive device 101(1) byinserting the distal tip of the core wire 114 into the filler material158.

Turning to FIG. 2B, in an alternative embodiment of a vaso-occlusivedevice 101(2), a bushing 196 is used to couple the core wire 114 to theprimary coil 102. Specifically, the proximal end of the primary coil 102is mounted within the distal end of the bushing 196, and the distal endof the core wire 114 is disposed within a mini coil 198, which in turn,is mounted within the proximal end of the bushing 196. The fillermaterial 158 is disposed in the proximal end of the lumen of the primaryand anchor coils and surrounds the core wire 114. The mini coil 198provides additional physical mass obstruction to which the fillermaterial 158 can adhere, thereby maintaining the tensile strength of themain junction between the primary coil 102 and the detachment means 112.

Referring to FIG. 2C, in another preferred embodiment of avaso-occlusive device 101(3), the stretch-resisting member 108 isindirectly attached to the primary coil 102 through an anchor assembly109(2) comprising an anchor chain 170 with two links, a proximal link172 and a distal link 174(1). The links may be in any form, e.g.,twisted or intersecting, that prevents the links from collapsing onthemselves such that the stretch-resisting member 108 is separated fromthe proximal end 104 and is not melted or otherwise damaged during themanufacturing of the coil assembly 100.

In the preferred embodiment illustrated in FIG. 2C, the proximal link172 is twisted. The proximal twisted link 172 is formed by twisting awire around itself and includes a closed loop 176 at its distal end, atleast one twist/intersection 178, and a sealed junction 180 in which thetwo ends of the wire have been melted together. In a preferredembodiment, a ball 182 that is formed at the sealed junction 180 as aresult of the melting process is used to increase tensile strength ofthe main junction between the primary coil 102 and the detachment means112. In the illustrated embodiment, the proximal link 172 is less thanabout 2.6 mm, preferably about 1.2 mm in length.

In this preferred embodiment, a bushing 196 is used to couple the corewire 114 to the primary coil 102. Specifically, the proximal end of theprimary coil 102 is mounted within the distal end of the bushing 196.The core wire 114 is mounted in the proximal end of the bushing in amanner similar to that discussed with reference to FIG. 2B. The ball182, located just distal of the proximal end 104 or the primary coil102, is also contained within the bushing 196, surrounded by fillermaterial 158. As with the mini coil 198, the ball 182 providesadditional physical mass obstruction to which the filler material 158can adhere, thereby maintaining the tensile strength of the mainjunction between the primary coil 102 and the detachment means 112. Inan alternative embodiment, the proximal end of the primary coil 102 maybe crimped around the base of the ball 182 (not shown), therebyincreasing the tensile strength of the anchor.

In the embodiment illustrated in FIG. 2C, the distal link 174(1) is alsotwisted, which like the proximal link 172, is formed by twisting a wirearound itself and includes a closed loop 186, at least onetwist/intersection 188, and a sealed juncture 190 in which the two endsof the wire have been melted together. A ball 192 is formed at thesealed junction as a result of the melting process. In the illustratedembodiment, the distal link 174(1) is shorter than the proximal link172, preferably about 0.8 mm long. The distal link 174(1) may beconnected to the proximal link 172 by interconnecting or loopingtogether their closed loops 176 and 186, forming a flexible joint in theanchor assembly 109(2). The stretch-resisting member 108 is attached tothe distal link 174(1) through any appropriate means, including loopingthe stretch-resisting member 108 through or around the distal link174(1) or tying the stretch-resisting member 108 to the distal link174(1).

The links 172, 174 may be made from the same material used to make thevaso-occlusive coil 102, including the Platinum Group metals, especiallyplatinum, rhodium, palladium, rhenium, as well as tungsten, gold,silver, tantalum, and alloys of these metals. Suitable polymers may alsobe used. These include most biocompatible materials that may be madeinto fibers, including thermoplastics, e.g., polyesters such as Dacron;polyamides, including the Nylons; polyolefins, such as polyethylene,polypropylene, polybutylene, their mixtures, alloys and block. Althoughonly two links are depicted in FIGS. 2C, additional links may beinserted between the distal 174 and proximal 172 links as desired. Theanchor chain 109(2) formed from the links 172, 174 provides for a moreflexible means to attach the stretch-resisting member 108 indirectly tothe vaso-occlusive coil 102.

In this preferred embodiment, a bushing 196 is used to couple the coreire 114 to the primary coil 102. The proximal end of the primary coil102, with the ball joint 182 extending therefrom, is mounted within thedistal end of the bushing 196, and the distal end of the core wire 114is disposed within a mini coil 198, which in turn, is mounted within theproximal end of the bushing 196. The filler material 158 is disposedwithin the coil lumen 105 surrounding the proximal end of the proximallink 172 and around the ball joint 182 and mini coil 198 to stabilizeand enhance the structural integrity of the junction between thedetachment means and the vaso-occlusive coil device 101(3).

Although the distal link 174(1) of the anchor assembly 109(2) is shownas being twisted, an untwisted distal link can be used. For example,referring to FIG. 2D, an anchor assembly 109(3) of a vaso-occlusivedevice 101(4) uses an untwisted distal link 174(2). Similar to theembodiment described in FIG. 2A, the distal link 174(2) may be formed byheating/welding the wire to close the loop, or it may be a laser cutpiece. As depicted in FIG. 2D, the distal link 174(2) is shorter thanthe proximal link 172, preferably about 0.8 mm long. The distal link174(2) can be composed of the same material and can be connected to theproximal link 172 and stretch-resisting member 108 in the same manner asdescribed with respect to the distal link 174(1) in vaso-occlusivedevice 101(3).

Referring to FIG. 3, a vaso-occlusive assembly 200 constructed inaccordance with another preferred embodiment is described. Like theafore-described vaso-occlusive assembly 100, the assembly 200 includesthe elongate delivery device 116, which includes the detachable means112 and associated slidable core wire 114. The assembly 200 differs inthat it includes a vaso-occlusive device 201. The device 201 includes anouter primary coil 202, which has a proximal end 204, a distal end 206,and a lumen 205 extending therethrough. The vaso-occlusive device 201further includes a stretch-resisting member 208, which extends throughthe coil lumen 205 and is secured to the primary coil 202 at twolocations to prevent axial stretching of the primary coil 202.Specifically, the proximal and distal ends of the stretch-resistingmember 208 are respectively affixed to the distal and proximal ends 102and 104 of the primary coil 202. Alternatively, the proximal and distalends of the stretch-resisting member 208 may be attached to one or morelocations between the proximal and distal ends 204 and 206 of theprimary coil 202. At the proximal end 204, the vaso-occlusive device 201includes an anchor assembly 209 fixedly coupled to the primary outercoil 202. The proximal end of the stretch-resisting member 208 isindirectly attached to the proximal end 204 of the outer coil 202through the anchor assembly 209, and specifically, an anchor coil 232.As will be described in further detail below, the anchor coil 232 ismated with the primary coil 202, such that windings of the anchor coil232 are disposed in the space between adjacent windings of the primarycoil 202.

The primary coil 202, anchor coil 232, and stretch-resisting member 208can be composed of the same material and constructed in the same mannerpreviously described with respect to the corresponding elements in thevaso-occlusive device 101. The distal end of the stretch-resistingmember 208 can be fixedly attached to the coil 202 as previouslydescribed in the device 101, e.g., by reforming the distal end of thestretch-resisting member 208 into a distal cap 207 or by attaching thestretch-resisting member to some other location on the coil using anyappropriate means.

Referring to FIGS. 4A-4D, the primary coil 202 (shown in alternativeembodiments of FIGS. 4A and 4C as 202(1) and 202(2)) is similar to theprimary coil 102 used in the other preferred embodiments depicted inFIGS. 2A and 2B, except that the proximal end 204 of the primary coil202 is made to have an open pitch. The open pitch at the proximal end204 enables windings 216 from the anchor coil 232 (shown in alternativeembodiments of FIGS. 4B and 4D as 232(1) and 232(2)) to be incorporatedin the space 214 between consecutive windings 212 of the primary coil202. The spacing of the windings 212 at the proximal end 204 depends onthe number and thickness of windings 216 of the anchor coil 232 thatwill be disposed within each of the spaces 214.

Generally speaking, the anchor coil 232 is made such that it is similarin size (diameter) and properties to the outer primary coil 202. Thelength of the anchor coil 232 can be varied without sacrificingmechanical properties or performance in order to separate thestretch-resisting member 208 sufficiently from the proximal end duringmanufacture. In the illustrated embodiment, the anchor coil 232 is about2 mm long.

In the preferred embodiment, the windings 212 of the proximal end 204 ofthe primary coil 202 are spaced such that they conveniently accommodatethe size and number of the windings 216 of the anchor coil 232 withoutexerting a substantial axial stress to the windings of the primary coil202 and anchor coil 232.

For example, as illustrated in FIGS. 4A and 4B, an anchor coil 232(1)has a single winding open pitch, and windings 212(1) on a primary coil202(1) are spaced to accommodate a single winding 216(1) of the anchorcoil 232(1), such that each winding 216(1) of the anchor coil 232(1)easily fits between adjacent windings 212(1) of the primary coil 202(1).A loop 240(1) formed from the final turn or half-turn of the anchor coil232(1) is connected to the stretch-resisting member 208.

As another example, as depicted in FIGS. 4C and 4D, an anchor coil232(2) formed by one strand of wire has a double winding open pitch, andthe windings 212(2) on a primary coil 202(2) are spaced to accommodate adouble winding 216(2) of the anchor coil 232(2), such that each doublewinding 216(2) of the anchor coil 232(2) easily fits between adjacentwindings 212(2) of the primary coil 202(2). A loop 240(2) formed fromthe final turn or half-turn of the anchor coil 232(2) provides thethreaded loop for the stretch-resisting member 208.

Although only anchor coils having single and double winding open pitcheshave been described, anchor coils of other varying thickness and pitchmay be incorporated where the proximal end of the outer coil has beenformed such that the spacing between adjacent windings can accommodatethe size and number of the anchor coil windings.

As illustrated in FIGS. 5A and 5B, the anchor coil 232 (shown inalternative embodiments of FIGS. 5A and 5B as 232(1) and 232(2)) isinserted into the proximal end 204 of the primary coil 202 (shown inalternative embodiments of FIGS. 5A and 5B as 202(1) and 202(2)) bytwisting the distal end 240 of the anchor coil 232 into the lumen 205 ofthe primary coil 202, such that the windings 216 from the anchor coil232 are situated in the space 214 between adjacent primary coil windings212. Insertion of the anchor coil 232 can be facilitated by tapering thedistal end 226 of the anchor coil 232. The anchor coil 232 is inserteduntil the entirety or substantially the entirety of the anchor coil 232is mated with the proximal end 204 of the primary coil 202.

The loop 240 located at the distal end 226 of the anchor coil 232 isconnected to the stretch-resisting member 208. The stretch-resistingmember 208 may be attached to the loop 240 through any appropriatemeans, including looping the stretch-resisting member 208 through oraround the loop 240 or tying the stretch-resisting member 208 through oraround the loop 240. The attachment of the stretch-resisting member 208to the loop 240 of the anchor coil 232 fixedly couples thestretch-resisting member 208 to the outer primary coil 202.

The screw mate connection of the anchor coil 232 to the outer primarycoil 202 provides additional flexibility at the proximal end,eliminating the “layered coaxial” stiffness of previous anchor assemblydesigns, by interconnecting the anchor coil 232 with the proximal end204 of the outer primary coil 202 rather than coaxially situating theanchor coil within the lumen 205 of the primary coil 202.

A filler material 250 is placed within the lumen 205 of the proximal endof the combined anchor coil 232 and primary coil 202 for stabilizationand to attach the device 201 to the core wire 114 via detachable means,in this case, an electrolytic joint 112. The filler material 250preferably comprises a thermoplastic formed into place or an epoxy orthe like and adheres in turn to the anchor coil 232, primary coil 202and the core wire 114. Preferably, the filler material 250 comprisesPET, polyamide, silicon, or polyurethane. Alternatively, the fillermaterial 250 may comprise a conductive filler material, such as anyalloy, conductive epoxy, or conductive polymer.

Referring to FIG. 6, a vaso-occlusive assembly 300 constructed inaccordance with another preferred embodiment is described. The assembly300 differs from the afore-described vaso-occlusive assemblies 100, 200in that it includes a vaso-occlusive device 301 with multiple primarycoils. For example, four coils 302(1)-(4) are illustrated in FIG. 6,with multiple severable joints 312(1)-(3). Specifically, multiple corewires 314(1)-(3) with electrolytically severable joints 312 are used todetachably connect the coils 302 to each other. Alternatively, theseverable joint may be tapered, coated with an insulative polymer andscored, or otherwise modified, such as described in earlier embodiments.

Specifically, the portion of the device 301 that is illustrated includesfour outer primary coils 302(1)-(4), each of which has a proximal end304, a distal end 306, and a lumen 305 extending therethrough. Thevaso-occlusive device 301 further includes four stretch-resistingmembers 308(1)-(4) that extend through each coil lumen 305(1)-(4) andare secured to the respective primary coils 302(1)-(4) at two locationsto prevent axial stretching of the primary coils 302(1)-(4).Specifically, the proximal and distal ends of the stretch-resistingmembers 308 are respectively coupled to the respective proximal anddistal ends 304 and 306 of the primary coils 302. Alternatively, theproximal and distal ends of the stretch-resisting members 308 may becoupled to one or more locations between the proximal and distal ends304 and 306 of the primary coils 302. As will be described in furtherdetail below, a selected number of the primary coils 302 may be releasedfrom the delivery device 116 by applying a current to the core wires 114to dissolve the proximal-most several joint 312 that is exposed to theionic environment.

The vaso-occlusive device 301 includes an anchor assembly 309 at theproximal end 304 of each of the primary coils 302. The anchor assembly309 may comprise any of the anchor assemblies discussed above in otherpreferred embodiments. The vaso-occlusive device 301 may optionallycomprise an anchor assembly 309 at the distal end 306 of each of theprimary coils 302. Therefore, in each of these segments (with theexception of the primary coil located at the distal end), there arepreferably two anchor assemblies coupled to each primary coil at itsproximal and distal ends. The stretch-resisting member 308 located inthe lumen 305 of the primary coil 302(1) at the distal end may bedirectly attached to the distal tip of the primary coil 302(1), asdiscussed previously with respect to vaso-occlusive device 101.

The anchor assemblies 309 and stretch-resisting members 308 can becomposed of the same material and constructed in the same mannerpreviously described with respect to the corresponding elements invaso-occlusive devices 101 and 201. The primary coils of this embodimentare preferably made from conductive material, such as Platinum,stainless steel, and nitinol.

Referring to FIGS. 7A-7E, variations of the anchor assemblies 309(1)-(5)used in the vaso-occlusive assembly 300 are illustrated. For example,the anchor assemblies 309 may include an anchor coil 150 with a distallink 152 (309(1); see FIG. 7A); an anchor chain with multiple links,where a proximal link 172 is twisted and a distal link is eitheruntwisted 174(1) (309(2); see FIG. 7B) or twisted 174(2) (309(3); seeFIG. 7C); or an anchor coil 232(1) and 232(2) mated with the primarycoil 302(a) and 302(b), such that the windings 216 of the anchor coil232 are disposed in the space between adjacent windings 212 of theprimary coil 302(a) and 302(b) (309(4) and 309(5); see FIGS. 7D and 7E).

For the embodiments depicted in FIGS. 7A-7C, each primary coil 302 hasbushings 196(a) and 196(b) located on its proximal and distal ends 304and 306 that are used to couple the core wires 314 to the primary coils302. Specifically, the proximal ends 304 of the primary coils 302 aremounted within the distal ends of the bushings 196(a), and the distalends of the core wires 314 are disposed within mini coils 198, which inturn, are mounted within the proximal ends of the bushings 196(a). Theinsulative filler material 158 is placed in the coil lumen 305 of theproximal end 304 of the primary coils 302 for stabilization and toattach the primary coil 302 and anchor assembly 309 to the core wire314. Similarly, the distal ends 306 of the primary coils 302 are mountedwithin the proximal ends of the bushings 196(b), and the proximal endsof the core wires 314 are disposed within mini coils 198, which aremounted within the distal ends of the bushings 196(b). A conductivefiller material 358 is placed in the coil lumen 305 of the distal end306 of the primary coils 302 for stabilization and to attach the primarycoil 302 and anchor assembly 309 to the core wire 314. As described in aprevious embodiment, the mini coil 198 provides additional physical massobstruction to which the filler materials 158, 358 can adhere, therebymaintaining the tensile strength of the main junctions between theprimary coils 302 and the core wires 314.

For the embodiments depicted in FIGS. 7D-7E, the core wires 314 arecoupled to each primary coil 302(a) and 302(b) without the use ofbushings. Specifically, the distal ends of the core wires 314 are heldin the coil lumens 305 of the proximal ends 304 of the primary coils302(a) and 302(b) with the insulative filler material 158. The proximalends of the core wires are similarly held within the coil lumens 305 ofthe distal ends 306 of the primary coils 302(a) and 302(b) with aconductive filler material 358.

As previously described, the filler material 158 that connects thedistal ends of the primary coils 302 with the proximal ends of the corewires 314 is electrically insulative. Without wishing to be bound by atheory, it is believed that the electrical isolation of the severablejoint provided by this insulative filler material 158 prevents orlessens current flow through the outer coils 302 and concentratescurrent flow through the selected core wire 314. Therefore, theinsulative filler material 158 serves two primary functions. The firstis to electrically isolate the severable joint 312 so that electricalenergy is not transmitted to any part of the assembly 300 distal to theparticular link 312 selected for disintegration. In addition, the fillermaterial 158 also serves to reliably and fixedly join the severablejoint 312 and the outer coil 302. Preferably, as previously discussed,the insulative filler material 158 comprises a biocompatible,electrically insulative material such as Polyfluorocarbons (e.g.,Teflon), PET, polyproplene, polyurethane, polyimides, polyvinylchloride,silicone polymers, and Parylene. Other types of insulative materials arediscussed in U.S. Pat. No. 5,941,888, the entirety of which is hereinexpressly incorporated by reference.

Proximal of the severable joints 312, the electrically conductive fillermaterial 358 joins the distal ends 306 of the outer coils 302 with theproximal ends of the core wires 314. Preferably, as shown in FIGS.7A-7C, the conductive filler material 358 surrounds the core wire 314and is contained within the bushing 196(b) and the lumen 305 of theouter coil 302. The conductive filler material 358 provides anelectrical pathway between the core wire 314 and the bushing 196(b) andprimary coil 302 so that electrical current is readily transmitted tothe severable joint 302. Alternatively, as depicted in FIGS. 7D-7E,where there is no bushing, the conductive filler material 358 providesan electrically conductive pathway between the core wire 314 and theouter coil 302. Preferably, the conductive filler material 358 comprisesany biocompatible, electrically conductive material, preferably aconductive particle-filled polymer, such as PET with gold flakes, or asuitable metal such as platinum or nitinol, as described in U.S. Pat.No. 5,941,888, the entirety of which has previously been incorporated byreference.

In an alternative embodiment, the core wire 314 is directly connected tothe primary coil, which is made from a conductive material (not shown).The conductive joint 370 may be assembled by welding, brazing,soldering, mechanically joining (e.g., crimping) or otherwiseappropriate means. Alternatively, the vaso-occlusive device may notcontain any insulative filler material, such that the core wires 314 aredirectly connected to the outer coils 302 at both its proximal anddistal ends.

The delivery catheter 317 is preferably equipped with an annular distalelectrode 324, partially embedded between a first tube 326 and a secondtube 328, as shown in FIG. 7. This electrode functions to conveyelectrical energy to selected severable joints 314. The electrode 324can be composed of any conductive biocompatible material. For examplethe electrode 324 can be comprised of conductive metals and their alloys(for example, steel, titanium, copper, platinum, nitinol, gold, silveror alloys thereof), carbon (fibers or brushes), electrically conductivedoped polymers or epoxies, or any combination thereof. In thisvariation, the electrode 324 and tubes 326 and 328 are preferablydesigned so that the electrode 324 and catheter lumen 330 present acontinuous, nonobstructed, smooth surface to allow vaso-occlusive deviceto pass smoothly out of the distal end of catheter 317. Such an annularconstruction maximizes the electrode's exposed surface area so as toincrease current flow efficiencies by avoiding too large a currentdensity passing therethrough. In the illustrated embodiment, the distalsurface of the electrode 324 is substantially flush with the distalsurface of catheter 317. However, other configurations wherein theelectrode 324 is spaced inwardly or outwardly from the distal surface ofcatheter 317 may also be used, as described in U.S. Pat. No. 5,941,888,the entirety of which has previously been incorporated by references.The counter electrode (not shown) may be connected to a needle that isinserted into the patient, e.g., in the groin area. Alternatively, thecounter electrode (not shown) may be an adhesive patch electrodeattached to the patient's skin.

The catheter 317 further comprises a conductor 334 that is coupled tothe electrode 324. The conductor 334, as illustrated in FIG. 7, is inthe form of an annular extension of the electrode 324. Alternatively,the conductor 334 can be in the form of a wire or ribbon whose distalend is coupled, e.g., by welding, to the electrode 324. The conductor334 extends from the electrode 324 between the tubular members 326 and328 to the proximal end portion of the catheter 317, where it can beelectrically connected to a power supply either directly or with a lead,as would be apparent to one of skill in the art. Alternativeelectrode-catheter arrangements are described in U.S. Pat. No.5,941,888, the entirety of which has previously been incorporated byreference.

Generally, the vaso-occlusive devices 101 and 201 described above aredelivered to an aneurysm within a blood vessel via a delivery catheter117. Referring to FIGS. 8A-8C, a method of deploying a vaso-occlusivedevice 101, and in this case, the primary coil 102, to the aneurysm 400via a delivery catheter 117 is illustrated. The vaso-occlusive device201 can similarly be delivered to the aneurysm 400 in the foregoingmanner, but for the purposes of brevity, only delivery of thevaso-occlusive device 101 will be described in detail.

Turning to FIG. 8A, the catheter 117 is steered to just within a neck402 of an aneurysm 400. At this point, the primary coil 102 is in itsundeployed shape, and is coupled to the core wire 114 via theelectrolytically severable joint 112. The vaso-occlusive device 101extends through the lumen of the delivery catheter 117 such that theprimary coil 102 is positioned at the distal end of the deliverycatheter 117.

Turning to FIG. 8B, the core wire 114 is then pushed toward the distalend of the catheter 117, causing the primary coil 102 to extend out ofthe distal end of the catheter 117, through the neck 402, and into theaneurysm 400. As the primary coil 102 is pushed out of the catheter 117,the portion of the primary coil 102 that is free from the constraints ofthe catheter 117 can assume its deployed shape, e.g., the coil 102 formsa secondary shape such as a cylinder.

Turning now to FIG. 8C, the core wire 114 continues to push the primarycoil 102 out of the catheter 117 until the proximal end 104 of theprimary coil 102 is deployed within the aneurysm 400. To release thecoil 102 from the delivery device 116, a current is applied to the corewire 114, which causes the joint 112 to dissolve, separating thevaso-occlusive device 101 from the proximal end of the delivery device116. Further discussion of the construction, placement, and otherphysical details of such electrolytically severable joints may be foundin U.S. Pat. No. 5,122,136 to Guglielmi et al.; U.S. Pat. No. 5,354,295to Guglielmi et al.; and U.S. Pat. No. 5,624,449 to Pham et al.

Depending on constraints such as the condition and size of the aneurysm,the physician may desire to use vaso-occlusive coils of varying length.Instead of having to deploy numerous coils into the aneurysm, avaso-occlusive device with multiple primary coils connected via multipledetachment sites allows the physician to vary the length of thevaso-occlusive device as needed.

Turning to FIG. 9A, where the vaso-occlusive assembly 300 containsmultiple detachment points 312, the catheter 317 is steered to justwithin the neck 402 of the aneurysm 400, as described previously. Atthis point, the multiple primary coils 302 are in their undeployedshape, and are coupled to core wires 314 via electrolytically severablejoints 312. The vaso-occlusive devices extend through the lumen of thedelivery catheter 317 such that the primary coil 302(1) is positioned atthe distal end of the delivery catheter 317.

Turning to FIG. 9B, the core wire 314 is then pushed toward the distalend of the catheter 317, causing the primary coil 302(1) to extend outof the distal end of the catheter 317 through the neck 402, and into theaneurysm 400. As the primary coil 302 is pushed from the catheter 317,the portion of the primary coil 302 that is free from the constraints ofthe catheter 317 can assume its deployed shape.

Turning now to FIG. 9C, when the physician has determined that theaneurysm 400 is sufficiently filled with vaso-occlusive device 301(usually using visualization techniques that are well known in the art),the vaso-occlusive device 301 may be detached from the delivery device316. To release the desired number of devices 301 from the deliverydevice 316, the physician positions the device such that the desiredseverable joint 314 is positioned just distal of the distal end of thecatheter 317, and thus, the annular electrode 324. A current is appliedto the core wire 314 via the conductor 334 and the electrode 324, whichis in contact with the conductive bushing 196(b) or conductive outercoil 302(1) and 302(2). This causes the proximal-most severable joint312 that is exposed to the ionic environment to dissolve, separating thevaso-occlusive device 301 from the delivery device 316.

Where the core wires 314 are directly coupled to the outer coils 302with no insulative joints, there are multiple severable joints 312 inthis embodiment that are exposed to an ionic environment in the aneurysm400. The proximal-most severable joint 312 that is exposed to the ionicenvironment, however, will preferably dissolve first. Presumably, thisis because it is closest to the power source and will receive the mostcurrent. Other methods of detachment are described in U.S. Pat. No.5,941,888, the entirety of which has previously been incorporated byreference.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

1. A vaso-occlusive device, comprising: a primary coil having a proximalend, a distal end, and defining an axial lumen; a stretch-resistingmember coupled to the primary coil and extending through at least aportion of the primary coil lumen; and an anchor assembly coupled withthe primary coil and to the stretch resisting member, the anchorassembly comprising an anchor coil having windings that are disposedbetween windings of the primary coil.
 2. The device of claim 1, whereinthe anchor coil is directly attached to the stretch-resisting member. 3.The device of claim 1, wherein each winding of the anchor coil isdisposed between adjacent windings of the primary coil.
 4. The device ofclaim 1, wherein at least two windings of the anchor coil are disposedbetween adjacent windings of the primary coil.
 5. The device of claim 1,wherein the stretch-resisting member comprises at least one polymericfilament.
 6. The device of claim 1, wherein a distal end of thestretch-resisting member is coupled to the distal end of the primarycoil and a proximal end of the stretch-resisting member is coupled tothe anchor coil.
 7. The device of claim 6, wherein the distal end of thestretch-resisting member is directly attached to the distal end of theprimary coil.
 8. The device of claim 1, wherein the anchor assembly iscoupled to the proximal end of the primary coil.
 9. The device of claim1, further comprising a deployment mechanism coupled to the proximal endof the anchor coil.
 10. The device of claim 9, wherein the deploymentmechanism comprises an electrolytically severable junction adapted todetach from a core wire by imposition of an electrical current on thecore wire.
 11. The device of claim 1, wherein all of the windings of theanchor coil are disposed between the windings of the primary coil. 12.The device of claim 1, the anchor coil further comprising an attachmentmember at a distal end of the anchor coil, wherein a proximal end of thestretch-resisting member is secured to the attachment member.
 13. Thedevice of claim 1, further comprising a plurality of primary coils, eachhaving a proximal end, a distal end, and each defining an axial lumen;and a plurality of stretch-resisting members, each extending through atleast a portion of a respective primary coil lumen.
 14. A catheterassembly for occluding a body cavity, comprising: a delivery devicehaving a distal end; and a vaso-occlusive device associated with thedistal end of the delivery device, the vaso-occlusive device comprisinga primary coil having a proximal end, a distal end, and defining anaxial lumen, a stretch-resisting member coupled to the primary coil andextending through at least a portion of the primary coil lumen, and ananchor assembly coupled with the primary coil and to the stretchresistant member, the anchor assembly comprising an anchor coil havingwindings that are disposed between windings of the primary coil.
 15. Thecatheter assembly of claim 14, wherein each winding of the anchor coilis disposed between adjacent windings of the primary coil.
 16. Thecatheter assembly of claim 14, wherein at least two windings of theanchor coil are disposed between adjacent windings of the primary coil.17. The catheter assembly of claim 14, wherein a distal end of thestretch-resisting member is coupled to the distal end of the primarycoil and a proximal end of the stretch-resisting member is coupled tothe anchor coil.
 18. The catheter assembly of claim 17, wherein thedistal end of the stretch-resisting member is directly attached to thedistal end of the primary coil.
 19. The catheter assembly of claim 14,wherein the anchor assembly is coupled to the proximal end of theprimary coil.
 20. The catheter assembly of claim 14, wherein all of thewindings of the anchor coil are disposed between the windings of theprimary coil.